Process of manufacturing soft absorbent pulp from sugar-cane, cornstalks, sorghum, and analogous pithy stalks and product of such process.



UNITED PATENT oFFIoE.

VIGGO DREW SEN, OF NElV YORK, N. Y.

PROCESS OF MANUFACTURING SOFT ABSORBENT PULP FROM SUGAR-CANE, CORNSTALKS, SORGHUM, AND ANALOGOUS PITHY STALKS AND PRODUCT OF SUCH PROCESS.

Specification of Letters Patent.

Patented Sept. 5, 1905.

Original application filed September 29, 1904, Serial No. 226,446. Divided and this application filed May 4, 1905. Serial No. 258,881.

f0 0 77 whom it in/u/ concern.-

Be it known that I, VIoGo DREWSEN, a citizen of the United States of America. residing in the city of New York, county of Kings, and State of New York, have invented a new and useful process of manufacturing soft absorbent pulp from sugar-cane, cornstalks, sorghum, and analogous pithy stalks and the product arising from such process, of which the following is a specification.

The difficulty in preparing fibrous material (cellulose) and other products suitable for the manufacture of paper from these pithy stalks lies in the different character of the different parts of the stalk. A cornstalk propernamely, without leaves or husks -f'or instance, consists of two parts which can be used by paper manufacturer-s te wit, the outside shell and the pith. The shell has a character similar to wood and contains a high percentage of fibers, while the .pith is spongy and consists principally of oblong cells. This is also true of the sugarcane and analogous plants. The shell when treated with chemical substances such as caustic soda and sodium sulfid, for instance yields a large proportion of fibers which are adapted for paper-making and produce an opaque sheet of paper. The pith, on the other hand, when treated with the same chemical substances disintegrates into cells, and the sheet of paper derived therefrom is translucent and constitutes parchment paper. Attempts were made long ago to utilize the stalks in the manufacture of paper by treatment with a caustic alkali, and in carrying out these attempts various processes were used, the earliest of which consisted in boiling the stalks, after having crushed them, in a weak solution of caustic soda for about six hours. The result was a parchment-like more or less discolored brittle paper which had few uses, and the processes never led to any prac tical manufacturing result. It was therefore supposed that the difference in character between the fibers of the shell and the cells of the pith required two separate cooking operations, wherein the fibers of the shell needed a stronger solution and a longer time for cooking than were needed for the pith, and it was also thought thatif the pith was cooked simultaneously with the shell in the same strength of liquor and for the same length of time as are required for the disintegration of the fibers of the shell and their separation from the incrustaceous matter the cells of the pith are practically destroyed and cannot be utilized. In a previous application for United States Letters Patent, filed by meJuly9, 1903, Serial No. 16i,759, however, I have described and claimed my discovery that this is not always the case, and that by the use of proper means only a single operation of cooking is necessary for the entire stalk, shell, and pith, and that both can be used either separately or together in making the paper. The papers made by this previous method of mine, while exceedingly useful. lacked some qualities which it was desirable to secure. for the pulp was not sufficiently absorbent and the paper consequently was not soft enough for the most desirable forms of paper for printers use and other purposes.

The object of my present invention is to secure these desired results, and l have made the discovery that by following the method hereinafter described the requisite qualities of paper can be obtained. The discovery is that if the stalks be cooked in a stronger solution and for a longer time than has heretofore been supposed to be possible without destroying the utility of the pith I succeed instead of' destroying the pith-cells in changing their parchment-like quality to a soft absorbent nature and in getting a superior quality of paper to any which has heretofore been produced from these substances, and the marked difference is illustrated by the fact that if paper heretofore produced from these substances is thereafter further cooked according to my discovery the quality of the paper will be quite changed, its hard character will be lost, and a paper is produced by this further cooking which has the requisite quality of softness.

In carrying out my process I first separate and cut up the entire stalk into pieces. This exposes the pith lying within the shell. (The cutting may be omitted, especially where the stalk has been crushed, as in rollers.) l have previously prepared a stock solution of caustic soda in water containing from live to ten per cent. of the caustic soda, by which is meant from ninety-live parts, by weight, of water to five parts, by weight,ofsoda up to ninety parts, by weight, of water to ten parts, by weight, of caustic soda, and this liquor is to be used in such quantities in the various cooking charges that the amounts of caustic soda in the solution may vary from fifteen to thirty per cent. of the bone-dry weight of the stalk being cooked. I then place these pieces of stalk in a digester or rotary containing thenecessary chemical solution say twenty per cent. (20%) of caustic soda, (Na2OH2O,) calculated from the bone-dry weight of the stalk, althoughI do not confine myself to this specific strength of the solution, for sodium sulfid (Nags) may be used in admixture with the caustic soda. Neither do I confine myself to the specific length of cooking time and steampressure given below, so long as the length of time of cooking, the strength of the cooking liquor, and the steam-pressure are sufficient to effect the change in the character of the pithcells, as above described. Cooking the stalk for nine hours at a steam-pressure of ninety pounds to the square inch has given satisfactory results. -After cooking the pieces of stalk the pressure is blown off or partially ofi from the digester or rotary and the contents are run out into a draining-vat, the dark-colored liquor is allowed to run off and is washed out of the solid material and saved to be used for special purposes, which form no part of this invention. The solid washed material, consisting of the cooked fibers and pith-cells, is then thrown on a screen to separate from it any part which may not have been thoroughly cooked and then can be run directly or after bleaching or filling or sizing onto the paper-machine, or the pulp may be used for other purposes than paper. By this method I avoid the necessity of using a beating-engine, for the cells are fine enough to replace the beaten fibers of other methods.

It is essential to my invention that the cooking liquor must contain a caustic alkali which is not a salt, but a base, and that the cooking be conducted under a greater pressure than atmospheric pressure, and that the cooking be conducted for a longer time than has heretofore been practiced. Of course some latitude may be allowed to the operator, for if the strength of the cooking liquor be much increased the time of cooking may be thereby somewhat lessened; but the desirable results which I have obtained will not be realized unless the fibers and pith-cells are cooked substantially longer and in a stronger cooking liquor than has heretofore been thought to be desirable or possible, and this longer cooking and stronger solution give a totally different quality of pulp from that heretofore produced by former methods, including my own. What I mean by a stronger cook ing liquor is one which contains from five to ten per cent. of the caustic alkali, calculated to the weight of water employed.

The pulp described is useful not only for making paper therefrom, but for all purposes in which a pure cellulose is desired-such as I various combinations of'matter employed in the arts, such as composition balls, childrens toys, combs, brushes, toilet articles, &c.

This application is a divisionof the application filed by me on September 29, 1904, Serial No. 226,446, which was allowed April 19, 1905, and which was issued in United States Letters Patent No. 789,416, dated May 9,1905.

Having now described my invention, what I claim herein is 1. The new pulp produced from sugar-cane, cornstalks and analogous pithy stalks which consists of the disintegrated fibers of the shell of such stalk freed from their incrustaceous matter in admixture with the altered pithcells freed from their incrustaceous matter, and in which the pith-cells have been changed from a parchment-like, grease-repellent character to a soft, absorbent nature, substantially as described.

2. The new pulp produced from sugar-cane, cornstalks and analogous pithy stalks consisting of the altered pith-cells of said stalks freed from their incrustaceous matter and changed from their parchment-like, greaserepellent character to a soft, absorbent nature, substantially as described.

3. The process of producing soft, absorbent pith-cells from sugar-cane, cornstalks, and analogous pithy stalks freed from their incrustaceous matter (in contradistinction to parchment like, grease repellent pith cells) which consists incooking the stalks in a closed vessel under steam-pressure in a cooking liquor containing from fifteen to thirty per cent. of caustic soda, calculated from the bonedry weight of the stalk, for from four to ten hours according to the strength of liquor employed and under a steam-pressure of from sixty to one hundred pounds until the pithcells have been converted into soft, absorbent pulp instead of parchment-like, Water and grease repellent pulp, substantially as described.

VIGGO DREWSEN.

Witnesses:

MoRRIs GUITZLER, OTTO J. CHRIST. 

